Finding games…
IO games use compact ideas that can become absorbing contests: grow while avoiding larger opponents, claim territory, survive an arena or aim for the top of a leaderboard. The browser format makes it easy to explore different versions of those ideas. Check the game's own mode selection if playing against people is important to you. Different formats reward different habits. Growth games ask when to take a risk; shooters combine movement with aiming; territory games ask you to protect what you already control. Choose the kind of contest you enjoy, then check the controls and connection requirements before joining a longer session.
Look at the selected game's multiplayer options before inviting a friend.